Primer compositions

ABSTRACT

Adhesion of thermoplastic elastomers, such as unvulcanized styrene-butadiene rubber, to a solid substrate is obtained by using a primer containing a tackifier component, such as hydrogenated rosin or a coumarone-indene resin, and an aminofunctional trihydrolyzable silane, partial condensates and hydrochloride salts thereof in which the amino-functionality is in the form of a primary or secondary amine.

United States Patent [191 Plueddemann Apr. 30, 1974 PRIMER COMPOSITIONS [75] Inventor: Edwin P. Plueddemann, Midland,

Mich.

[73] Assignee: Dow-Coming Corporation, Midland,

Mich.

[22] Filed: Jan. 10, 1972 [21] Appl. No.: 216,769

[56] References Cited UNITED STATES PATENTS 3/1972 Strack 260/41.5 A X 8/1955 Speier 260/4482 N 2,721,873 10/1955 MacKenzie 106/218 3,545,991 12/1970 Body 106/218 3,317,577 5/1967 Ryan 260/4482 N 3,560,543 2/1971 Plueddeman 260/4482 N 3,554,952 l/l971 Plueddeman 260/4481 N Primary ExaminerTheodore Morris Attorney, Agent, or Firm-Norman E. Lewis [57] ABSTRACT 6 Claims, No Drawings PRIMER COMPOSITIONS The present invention relates to improved primer compositions. In one aspect, the invention relates to articles incorporating an unvulcanized elastomer adhered to a solid substrate.

Organofunctionalsilanes have been suggested as primers to improve the adhesion of elastomers and sealants to solid substrates. The bonds obtained by the use of such silane primers are not completely water resistant. The silane may be irreversibly bonded to the rubbery polymer through the organofunctional substituent, but the bonding to the substrate is through hydrolyzable substituents. Hydrolysis with hydrophilic substrates is reversible. As individual bonds are hydrolyzed, the polymer segments pull away from the interface and the silanol functionality is no longer available for reformation of chemical bonds with the substrate. Hydrolysis thus becomes irreversible and additional bonds are hydrolyzed until there is complete loss of adhesion;

The present invention provides water resistant bonding of rubbery polymers to hydrophilic solid substrates by use ofa primer'composition containing a tackifier resin and a silane having specific amine functionality. The primer is partially compatible with the elastomer, forms a hard but flexible film at the interface and provides chemical bonding to the substrate by means of relatively immobile silanol functionality. Although silanes have been used alone as primers or in combination with hot melt adhesives as described in the German Offenlegungsschrift No. 2,029,703, the concept of the above-described primer is believed to be novel.

Thus, it is an object of the present invention to provide an improved primer composition.

It is another object of the invention to provide a composite article having a rubbery polymer bonded to a solid substrate.

These and other objects of the present invention will be apparent to one skilled in the art upon consideration of the following disclosure and appended claims.

In accordance with the invention there is provided a priming composition comprising (a) 80 to 99.99 weight percent of a tackifier component consisting essentially of resin having a molecular weight of no more than 12,000, said resin being selected from the group consisting of natural or modified rosin, esters of natural or modified rosin,- polyterpenes, coumaroneindene resins and modified coumarone-indene resins, polycyclopentadiene, aliphatic hydrocarbon resins and chlorinated aliphatic hydrocarbon resins, asphaltic resins, polystyrene and copolymers of styrene with at least one ethylenically unsaturated aromatic monomer, phenolic and modified phenolic resins and chlorinated terphenyl or diphenyl resins having a chlorine content of about 42 to 65 weight percent; and (b) 0.01 to weight percent of an organosilicon compound of the general formula partial condensates thereof and hydrochloride salts thereof in which X is the hydroxyl group or a hydrolyzable radical; Q is a divalent hydrocarbon radical or a groups wherein R is a hydrogen atom, a lower alkyl group containing from one to six inclusive carbon atoms, or a phenyl radical; and R is selected from the group consisting of the hydrogen atom, monovalent hydrocarbon radicals containing from one to 18 inclusive carbon atoms and oxygen-substituted monovalent hydrocarbon radicals containing from one to 18 carbon atoms.

The tackifier components present in the abovedescribed composition are well-known materials and are commercially available from a number of sources. Rosin, of course, is a component of the resinous exudation of various types of pine trees and consists essentially of abietic and similar type acids. Rosin is modified by hydrogenation to decrease the amount of unsaturation; by disproportionation to increase the dehydroabietic acid content; by polymerization to obtain a dimeric mixture and by reaction with fumaric acid or maleic anhydride. Both natural and modified rosin can be esterifled by reaction with glycerol, pentaerythritol glycols and other polyols. The readily available modified and esterified rosins include pentaerythritol ester of hydrogenated rosin, epoxidized pine gum, dichlorocarbene adductsof rosin ester, oxonated rosin, rosinformaldehyde adducts, disproportionated rosinpropylene glycol ester, diethylene glycol ester of beta-propiolactone-modified gum rosin, diethylene glycol ester of beta-propiolactone-modified gum rosin and maleic anhydride, alkyl diester of rosin and the betahydroxy alkyl ester of rosin.

Polyterpenes form another class of tackifiers. These materials are formed by the catalytic polymerization of alpha-and beta-pinenes which occur in turpentine and are considered as low molecular weight'polymers of isoprene (C T-I .The polymers can be linear or cyclic and generally have a molecular weight of less than 2,000. Coumarone and indene occur in the solvent naptha cuts of coal-tar distillates and are conveniently copolymerized in the presence of sulfuric acid to obtain coumarone-indene resins. Because of the residual unsaturation in these low molecular weight polymers, the materials can be reacted with aldehydes to provide fulvene-modification of the resin. The coumarone-indene polymers can also be hydrogenated, reacted with phenols or reacted with dicyclopentadiene. Cyclopentadiene, like coumarone and indene, is found in coal-tar and polymerizes at temperatures above 200C. to form a low molecular weight (500 to 600) resin.

Other suitable tackifiers include aliphatic hydrocarbon resins and resins derived from chlorinated hydrocarbon resins. These hydrocarbon and chlorohydrocarbon resins are relatively low molecular weight polymers derived from olefins and diolefms having three to five inclusive carbon atoms, such as n-butene and isobutylene. Exemplary are polybutenes having molecular weights in the range of 300 to 1,500 and polyisobutylenes having molecular weights in the range of 8,000 to 12,000. Also suitable are styrene homopolymers and styrene copolymers containing at least one ethylenically unsaturated monomer, such as vinyl toluene and alpha-methylstyrene. These hydrocarbon tackifier resins; aliphatic and aromatic, generally have a ring and ball softening temperature of from about 50 to C. Phenolic tackifiers include the phenol-formaldehyde novolac products, substituted products, such as palkylphenol novolac; phenol-furfural reaction products, p-tert-butylphenol-acetylene resins and phenoplasts based on the reaction of formaldehyde with substituted phenols such as p-cresol, p-tert-amyl phenol, p-phenylphenol and Bisphenol-A. The chlorinated terphenyl and diphenyl polymers useful as tackifiers have a chlorine content of from 42 to 65 weight percent and are yellow clear resins.

The above-described tackifiers are blended with amino-functional silanes in which the amine-function contains an active hydrogen. These silanes are of the general formula in which X, Q and R are as defined above. The hydrolyzable radicals in the definition of X include halogen atoms, for example, F, Cl, Br or 1; groups of the'formula OZ when Z is any hydrocarbon or halogenated hy- .bon or halogenated hydrocarbon radical such as those shown for Z above and M in any divalent hydrocarbon radical both valences of which are attached to the carbon, such as hexylene, pentylene or octylene; ureido groups of the formula N(M)CONM in which M is defined above and M" is H or any of the M radicals; carbamate groups of the formula OOCNMM" in which M and M are defined above, or carboxylic amide radicals of the formula NMC=O(M") in which M and M" are defined above. X can also be the sulfate group or sulfate ester groups of the formula OSO (OM) where M is defined above; the cyano group; the isocyanate group; and the phosphate group or phosphate ester groups of the formula -OPO(OM) in which M is defined above.

The term hydrolyzable group means any group attached to .the silicon which is hydrolyzed by water at room temperature to form silanols. Alkoxy radicals containing no more than four carbon atoms are the preferred hydrolyzable groups. 4

Q can be a divalent hydrocarbon radical or a divalent hydrocarbon radical containing one or more N(R) groups wherein R is a hydrogen atom, a lower alkyl radical containing from one to six inclusive carbon atoms or a phenyl radical. Specific examples of such divalent hydrocarbon radicals include, propylene, the +CH radical, the (-CH radical, the '-(-CH radical and branched chain radicals such as CHzCCHz-.

LII

The nitrogen-containing Q radicals are exemplified by Cl-l NHCH CH It is preferred that the div alent Q radical be free of aliphatic unsaturation and contain no more than 18 carbon atoms.

In addition to the hydrogen atom, R can be any monovalent hydrocarbon radical containing from one to 18 inclusive carbon atoms, such as alkyl radicals, such as methyl, ethyl, isopropyl, hexyl, octadecyl or myricyl; alkenyl radicals such as vinyl, allyl, hexenyl; alkynyl radicals such as propargyl', cycloaliphatic radicals such as cyclopentyl, cyclohexyl or cyclohexenyl; aromatic hydrocarbon radicals such as phenyl, tolyl, xylyl, xenyl, naphthyl or anthracyl and aralkyl hydrocarbon radicals 0 such as benzyl, beta-phenylethy], beta-phenylpropyl or gamma-tolylpropyl.

R can also be a substituted monovalent hydrocarbon radical containing oxygen in the form of -COC- or for example, omom o (5:

and the like.

' Thus the silanes useful in the present invention include ClaSiCHzC m@micincmp o C=CH2.

0 HaO)aSiC memo momma-@c H=CH2,

.lyzable groups remain uncondensed in the composition, preferably at least one such group per every four silicon atoms remains uncondensed. The partial condensate is a water-soluble polymer of SiOSi units with the silicon. atoms retaining their aminefunctionality, the hydroxylv or hydrolyzable groups being available for bonding with the'substrate.

These primer compositions can be prepared by cold blending the silane with the tackifier component in a mutual solvent. The silane is present in an amount in the range of from 0.01 to 20 percent by weight, based on the weight of primer composition excluding solvent. The optimum silane content will vary with the type of tackifier used and the elastomer to which it is applied.

For ease of application to solid substrates, it is pre-' ferred vto include a solvent, such as xylene or chloroform, in the primer composition.

The above-described primer compositions are utilized to increase the adhesion of rubbery polymers to solid substrates. The rubbery'polymers or unvulcanized thermoplastic elastomers are linear polymers, of natural or synthetic origin, having a glass transition temperature (Tg) of less than 0C. and a molecular weight of at least 20,000. Exemplary of such thermoplastic elastomers are unvulcanized natural rubber, chlorinated natural rubber, styrene-butadiene rubber, polyisoprene, butadiene polymers, polybutene, isobutyleneisoprene copolymers, ethylene-propylene copolymers and terpolymers, chlorinated butylene-isoprene polymers, chlorosulfonated polyethylene, polychloroprene, polyacrylates, polymethacrylates, acrylonitrile-butadiene rubbers, hexafluoropropylenevinylidene fluoride rubbery copolymers, epichlorohydrin' homopolymers, and epichlorohydrinpropylene oxide rubbery copolymers. These rubbery polymers often contain fillers, such as silica and additives, for example, pigments, plasticizers and stabilizers.

The primer composition used in conjunction with a particular thermoplastic elastomer is chosen to be partially compatible, but not completely compatible, with the elastomer. This partial compatibility results in migration of the primer into the rubber to provide adhesion. Of course, complete compatibility or solubility of polyurethanes, 1

the primer in the rubber would result in removal of the primer from the bond interface and subsequent loss of adhesion. Vulcanization or complete crosslinking of the elastomer prior to or after contact with the primer reduces compatilibity and results in poor adhesion. Thus, the primer composition must be matched with the elastomer. This matching or determination of compatibility characteristics can be accomplished by conventional adhesion tests known in the art. The examples illustrate the matching of the primer compositions to the elastomer.

The primer compositions of the invention are coated onto the surface of the solid substrate to which bonding of the elastomer is contemplated. The primer coating can be applied by conventional methods, such as dipping, spraying, brushing and the like. If the primer is used as a very dilute solution, provision for drying of the coating and removal of at least a portion of the solvent should be made,

The solid substrates to which rubbery polymers are commonly bonded include wood, metal, glass, ceramics, masonry, stone and plastics, both thermoplastic and therrnosetting, such as epoxy resins, polycarbonate and polymethylmethacrylate. A common use of the rubbery polymers, such as butyl rubber, is as sealant between different substrates, such as between metal and glass as exemplified by automobile Windshields. The use of the primer compositions of the invention greatly enhances the adhesion of such sealants.

The following examples are illustrative of the invention delineated in the claims.

EXAMPLE 1 Several primer compositions were prepared by cold blending parts by weight of 50 percent solutions of various tackifiers in xylene with 5 parts by weight of N- beta-aminoethyl, gamma-aminopropyl trim'ethoxysilane. Glass microscope slides were coated with the different primer compositions and allowed to air dry. The primed glass'slides were pressed against heated styrenebutadiene-styrene block copolymers having a molecular weight in the range of from about 70,000 to 100,000 (commercially available from the Shell Oil Company under the designation Kraton 1102) for oneminute at C. Adhesion of the thermoplastic elastomer to the glass was determined after cooling to room temperature. Adhesion was rated on a scale of l to 4 with a rating of 1 indicating that the elastomer was easily stripped from the glass; 2 indicating that the adhesion was better than on unprimed glass but that the elastomer could be stripped from the glass without tearing; 3 indicating that the elastomer could be stripped from the glass with a strong steady pull and that there was occasional tearing of the elastomer; and 4 indicating cohesive failure of the elastomer during attempts to peel. If initial adhesion was good, a duplicate sample was soaked in water for three days and adhesion was again determined.

The tackifier component utilized in the primer compositions and adhesion ratings are set forth below:

Adhesion Of Elastomer To Glass Tackifier Present In The Primer Composition Containing l0 wt. H NCH Cl-l NH(CH ),Si(0CH=) After 3 Days Water Immersion Dry At Room Temperature These primer compositions were either incompatible or completely compatible with the styrene-butadienestyrene block copolynlg.

This example demonstrates the simple screening test utilized in determining partial compatibility of the primer composition in a particular elastomer. It is to be noted that the silane alone is not an effective adhesion promoter. The data for primers utilizing terpenemodified phenolics and the glycerine ester of hydrogenated rosin shows that optimum adhesion can be retained under wet conditions for long periods of time.

EXAMPLE 2 Primer compositions containing various types of silanes were prepared by cold blending the silanes with one of two types of tackifier to obtain a primer contain- Adhesion of elastomer to glass (dry at room temperature) With terpenemodified phenol novolac resin With vinyltoluene-a-methylstyrene copolymer as tackifier as tackifier Silane component of primer composition component component No silane 1 1 r 1 1 CHz=CCOOCH2-aSi(0CHa)a I CH3 e e 1 1 CHz-CC O OCHz2N CHz-a Si(0 CH -C1 CH3 3):

CHz=CHS1 O CH3): 1 1

O 1 1 Cfi2 CH-CHzO CHz aSi(OCHz)a f 1 1 HS-OH2aSi(OCH a ClCHzCH2CH2Si(O OHm l 1 1 1 c1cH@-cmcrnsi(0 CH3):

Adhesion of elastomer to glass (dry at room temperature) With vinyltol- With terpeneuene-a-methylmodified phenol styrene cogolynovolac resin mer as tac fier as teckifler Silnne component of primer composition component component ICHzCHzCHzSKO CH3); .Q 1 1 BrzCuHaSKOCHm 1 1 1 1 CH;0 CH2 3Si(OCHa)3 (CH3)zN-CH1S1(OCH:); 1 1

CH3NH CI I s1(O CH 3 3 NH2/CH:\SKOCZH5)3 4 4 H H 4 4 H(NCH2CH2)2sNCH2-3 Si(0 CH3):

f 4 4 CHzNHCHzCH2NH-\CHzSi(O CH3)a-HC1 9 10 I EXAMPLE 3 I These data show that use of the primer compositions of Primer compositions were formulated containing terh invention gives significant increase f the adhe pene modified phenol novolac. as the tackifier and sion of thermoplastic elastomers to a variety of sur- B-aminoethyl, gamma-aminopropyltriethoxysilane as faces the silane. The amount of silane in the primer composition was varied from 0.01 to parts by weight per 100 EXAMPLE 5 parts of tackifier. The primer compositions were ap- I plied to glass slides from a xylene solution. Several dif- M tures containing 10 weight percent of B-amino ferent types of thermoplastic elastomers were bonded ethyl, gamma-aminopl'opyltrlmethoxysila"e and to the primed glass by pressing for 1 minute at 1509C. l0 taining different tackifier resins were applied to glass sl- Adhesion was determined by the previously described ides from xylene solution. Various thermoplastic rubmethod except that wet adhesion was determined after bery polymers were adhered to the primed glass and 1 day in water. As shown below each elastomer rethe degree of adhesion was determined. The following quired a unique optimum level of silane in the primer primer compositions were found to give good to very composition. good (rating of 3-4) with the designated elastomers:

Adhesion of Elastomer to Glass Parts Silane .slyrrene'Bumdiene Styrene- I I Ethylene-Propylene Addegjei Styrene Block copolymer Butadiene Rubber Butvl Rubber lsogrene Rubber Terpolymer 100 Parts or Tackifier Dry Wet 1 Dry Wet Dry Wet Dry Wet Dry Wet 0 l l i l l 0.01 2 l 4 4 i l 1 0.05 4 2 4 4 l l 1 0i 4 I 4 4 4 2 2 2 l 0.5 4 4 4 4 2 4 2 l 1.0 4 4 4 4 2 2 3 2 l 2.0 i 4 g 4 4 4 4 4 4 4 2 2 5.0 4 4 2 l 4 3 4 3 4 2 10.0 4 2 l 4 3 4 2 4 4 These data demonstrate that, for certain elastomers, Elasmmer Primer Composition such as styrene-butadlene rubber, only very small 4 isoprene glycerlnc ester of hydrogenated amounts of silane n combination with the specified rosin plus aminosilane and polytackifier) are needed to obtain optimum adhesion chlom Tens P P g wfz lz i cerln while adhesion of other elastomers, such-as ethylenep i plug aminmilyaneg propylene terpolymers, requires much greater amounts y p y e P flmmvmldne of the silane when the same tackifier is utilized. It is evichlum'bmylenwsopwne dent that the amount of silane present in the primer fair" adhesion composition is a factor affecting compatibility with the "P block copolymer plus aminosilane elastomers. v ethyerlie-propylene polyterpene plus aminosilane er oymer chlorosulfonated polyvinyltoluene-alphu-methylstyrene 7 4 ethylene copolymer plus aminosilane acrylic vinyltoluene-alpha-methylstyrene copolymer plus aminosilane T 'F 'contammg 10 parts epichlorohydrin homopolymer terpene-modified phenolic novolac weight of silane as described in Example 3 was applied plus aminos ilane f a percent Xylene Solution to a variety of 45 epichlorohydrin-ethylene terpene-rnod fied phenolic novolac oxide copolymer plus aminosilane and vinyltoluene strates. Adhesion of a styrene-butadiene-styrene block alpha methylstyrene copolymer plus copolymer to the primed- Substrates was determined hexafluorovinyli I 5x2311 22? of hydrogenated rosin o f g ti j g li l to the P b f Substrate dene fluoride copolymer plus ilminosilane was a so e ermine esu ts are given e ow:

- I so This list is representative of primer compositions I f t T S b t w. M- Wmi, v. Adheslon 0 Omar s r matchedtothermoplastic elastomers to obtain adhe- Unprimed Primed 5 sion. I I V w t We Reasonable modification and variation are within the C substrate 1 Dry (3 days) Dry. (3 days) scope of the invention which is directed to novel primer I I compositions and the use of such primers in the bonding of thermoplastic elastomers. Glass 1 4 2 I claim: Ceramic Tile 2 1 4 4 l. A composition comprising a ggg 'f f g 1 a. 80 to 99.99 weight percent of a tackifier compo- Titanium 1 3 2-3 ncnt consisting essentially of resin having a molecgf t d s I g T 2 1 ular weight of no more than l2,000, said resin si iif s steel l l 3 3 being selected from the group consisting of natural Cold-rolled Steel 1 3 3 or modified rosin and esters of natural or modified Marble l Li Red Cedar l 5-5 mm; and E'oxyResin'Oii i 3 2 b. 0.01 to 20 weight percent of an organosllicon com- A uminum pound of the general formula water soluble partial condensates thereof and hydrochloride salts thereof in which X is the hydroxyl group or a hydrolyzable radical; Q is a divalent hydrocarbon radical or a substituted divalent hydrocarbon radical containing nitrogen in the form of groups wherein R is a hydrogen atom, a lower alkyl group containing from one to six inclusive carbon atoms or a phenyl radical; and

R is selected from the group consisting of the hydrogen atom, monovalent hydrocarbon radicals containing from one to 18 inclusive carbon atoms .and substituted monovalent hydrocarbon radicals containing oxygen in the form of and having from one to 18 inclusive carboniatoms.

2. The composition of claim 1 including a solvent for component (a).

in which X is an alkoxy radical containing from one to four inclusive carbon atoms.

6. A composition in accordance with claim 1 wherein component (b) is of the formula in which X is an alkoxy radical containing from one to four inclusive carbon atoms. 

2. The composition of claim 1 including a solvent for component (a).
 3. A composition in accordance with claim 1 wherein component (a) is selected from the group consisting of hydrogenated rosin and esters of hydrogenated rosin.
 4. A composition in accordance with claim 1 wherein the organosilicon compound is selected from the group consisting of X3SiCH2CH2CH2NH2 and X3SiCH2CH2CH2NHCH2CH2NH2 in which X is an alkoxy radical containing from one to four inclusive carbon atoms.
 5. A composition in accordance with claim 1 wherein component (b) is of the formula X3Si-CH2-3NHCH2CH2NHCH2- O -CH CH2 . HCl in which X is an alkoxy radical containing from one to four inclusive carbon atoms.
 6. A composition in accordance with claim 1 wherein component (b) is of the formula 